Python implementation of "Elliptic Fourier Features of a Closed Contour"
Project description
PyEFD
An Python/NumPy implementation of a method for approximating a contour with a Fourier series, as described in [1].
Installation
$ pip install pyefd
Usage
Given a closed contour of a shape, generated by e.g. scikit-image or OpenCV, this package can fit a Fourier series approximating the shape of the contour:
from pyefd import elliptic_fourier_descriptors
coeffs = elliptic_fourier_descriptors(contour, order=10)
The coefficients returned are the a_n, b_n, c_n and d_n of the following Fourier series representation of the shape.
The coefficients returned are by default normalized so that they are rotation and size-invariant. This can be overridden by calling:
from pyefd import elliptic_fourier_descriptors
coeffs = elliptic_fourier_descriptors(contour, order=10, normalize=False)
Normalization can also be done afterwards:
from pyefd import normalize_efd
coeffs = normalize_efd(coeffs)
To use these as features, one can write a small wrapper function:
def efd_feature(contour):
coeffs = elliptic_fourier_descriptors(contour, order=10, normalize=True)
return coeffs.flatten()[3:]
If the coefficients are normalized, then coeffs[0, 0] = 1.0, coeffs[0, 1] = 0.0 and coeffs[0, 2] = 0.0, so they can be disregarded when using the elliptic Fourier descriptors as features.
See [1] for more technical details.
Testing
Run tests with:
$ python setup.py test
or with Pytest:
$ py.test tests.py
The tests includes a single image from the MNIST dataset of handwritten digits ([2]) as a contour to use for testing.
Documentation
See ReadTheDocs.
References
v1.0 (2016-04-19)
Deemed stable enough for version 1.0 release
Created documentation.
v0.1.2 (2016-02-29)
Testing with pytest instead of nosetests.
Added Coveralls use.
v0.1.1 (2016-02-17)
Fixed MANIFEST
Added LICENSE file that was missing.
v0.1.0 (2016-02-09)
Initial release
Project details
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